experimental campaign, with the total auxiliary heating power of 4.5MW (ECRH/2MW,
NBI/1.5MW, and LHCD/1MW) and the effective SMBI technique, the physical
experiment was focused on confinement improvement of HL-2A plasmas from
L-mode to H-mode as well as particle transport, impurity transport, edge
plasma and turbulence and MHD instability. In April, the repetitive
H-mode discharges with Type-III ELM were successfully obtained for the
first time in HL-2A tokamak by combining high auxiliary heating power of
1.2 MW ECRH and 0.9 MW NBI under low toroidal magnetic field. It is also
the first time for domestic tokamak devices to obtain high confinement
operation mode, which has marked a milestone in the history of magnetic
confinement fusion experiment research in China. It indicates that great
progress has been made in the scientific research on exploitation of
magnetic confinement fusion energy in China, providing a platform for
advanced study in SWIP. Furthermore, a number of achievements were
obtained in the studies of HL-2A plasmas with high operation parameters,
as summarized as follows.
and edge and divertor physics: Edge transport barrier (ETB) was observed
in the edge region of H-mode plasmas with Type-III ELM. Material limit
in presence of ELM, ELM energy and particle transport from the
confinement region to the first wall, the time scale and deposition
position of ELM energy flux in the divertor region, were investigated.
and zonal flows (ZF): Peaked values of the low frequency zonal flows of
0~5 kHz and the geodesic acoustic mode (GAM) oscillations of 10 kHz were
simultaneously observed in the float potential spectrum for the first
time. Analysis confirmed that both ZF and GAM appear in the edge region
of HL-2A plasmas. The new discovery has been published in Phys. Rev.
a high temporal and spatial resolved fast scanning pneumatic-driven
Langmuir probe system, statistical character of blob with an
intermittent and coherent structure was analyzed in SOL. Probability of
blob existence in both time and space was preliminarily estimated to be
18% and the particle flux brought by blob was 58% of the total particle
fuelling method and related physics: the key technique of high-field
side SMBI injection was explored and density feedback control was
carried out using SMBI. Transport study was performed with the modulated
SMBI as a perturbation source. The existence of a localized particle
transport barrier, which is a new finding, was confirmed in both
experiment and simulation.
magnetohydrodynamic (MHD) instability: Neoclassical tearing mode (NTM)
was observed in HL-2A plasmas for the first time. Detailed analysis
suggested that the non-linear growth rate of magnetic island was in
agreement with the theoretical prediction. For the control of the NTM,
ECCD was applied to control large sawtooth generated by energetic ions
from neutral beam heating. It is a frontier topic in fusion research.
particle physics: During ECRH heating, a new type of Alfven mode excited
by energetic electron was observed for the first time. In NBI discharge,
the low-frequency ion fishbone of 10~15 kHz as well as other important
physical phenomena of energetic particles were newly found.